Applications for radio frequency identification systems

ABSTRACT

The present invention relates to RFID devices, including handheld RFID devices, and applications for such devices. The devices and applications may be used in connection with items that are associated with an RFID tag, and optionally a magnetic security element. The devices and applications are described with particular reference to library materials such as books, periodicals, and magnetic and optical media.

RELATED APPLICATIONS

This patent application is a division of application Ser. No.09/619,220, filed Jul. 19, 2000 now U.S. Pat. No. 6,486,780, which is adivision of application Ser. No. 09/368,826, filed Aug. 5, 1999 (nowU.S. Pat. No. 6,232,870), which is a continuation-in-part of U.S.application Ser. No. 09/344,758, filed Jun. 25, 1999 (now abandoned),which is a continuation-in-part of U.S. application Ser. No. 09/134,686,filed Aug. 14, 1998 (now abandoned).

INCORPORATION BY REFERENCE

This patent application claims priority from U.S. application Ser. No.09/134,686, filed Aug. 14, 1998 with the same title now abandoned, andU.S. application Ser. No. 09/344,758, filed Jun. 25, 1999 with the sametitle now abandoned, both of which were assigned to the assignee of thepresent invention, and the contents of both of which are incorporated byreference herein.

TECHNICAL FIELD

The invention relates to applications for radio frequency identification(RFID) systems, and particularly to the use of such systems inlibraries.

BACKGROUND OF THE INVENTION

Electronic article surveillance (“EAS”) systems detect the presence ofsmall electronic devices placed on or in an article or carried by aperson of interest, and are often used in retail or library environmentsto deter theft or other unauthorized removal of articles. These devices,which are commonly known as tags or markers, have in the past containedonly information regarding the presence of an item. This informationcould be obtained by electronically interrogating the tag, eitherintermittently or continuously. At least four distinct types of EASsystems have evolved over the years, based on how this interrogation wascarried out: magnetic, magnetomechanical, radio frequency (RF), andmicrowave. Of these four, magnetic systems have provided the highestlevel of security in most applications. Magnetic tags are easily hiddenin or on an object, difficult to detect (because they are lesssusceptible to shielding, bending, and pressure), and easy to deactivateand reactivate, thereby providing a high degree of security and someinformation regarding the status of the tagged article.

Many users of EAS systems desire to know more than just whether a taggedobject is present. They also want to know which tagged object ispresent, for example. Detailed information regarding the characteristicsof objects, such as their date of manufacture, inventory status, andowner have generally been communicated to automated handling and controlsystems through an optical bar code. While inexpensive and effective,the optical bar code system has certain limitations. Bar codes must bevisible, which limits the locations in which they may be placed, and barcodes can easily be obscured, either accidentally or intentionally. Therange at which a detector can sense the bar code is also comparativelysmall. The bar code may also have to be appropriately positioned fordetection. Also, because bar codes are often exposed to permitdetection, the barcode is susceptible to damage that can result indetection failures. Lastly, multiple items must be processed one at atime. These constraints of bar code systems make them undesirable orinefficient for some applications, such as marking library media.

More recently, electronic identification (also known as radio frequencyidentification or RFID) techniques have been developed to address thelimitations of optical barcodes. RFID systems have succeeded inproviding object identification and tracking, but are deficient inproviding object security because most RFID systems operate in frequencyranges (˜1 MHz and above) in which the tag is easily defeated. Thesecurity deficiency associated with radio frequency tags arises becausethey can be “shielded” by, for example, covering the tag with a hand oraluminum foil, or even placing the tag in a book. Even battery-poweredradio frequency tags may be blocked, although their range is superiorand blocking would be more difficult. Thus, objects tagged with an RFIDtag may escape detection, either inadvertently or intentionally. Thisgreatly reduces their effectiveness as security devices. RFID markersare also related to “smart cards.” Both contact and contactless smartcards have appeared in commercial applications. Smart cards tend to beassociated with a specific person rather than with a tagged object.Issues related to the security and tracking of the smart card (or of theperson carrying it) are similar to those discussed above for RFIDmarkers.

The security issues associated with RFID markers are similar to thosefamiliar to anyone skilled in the art of radio frequency- andmicrowave-based EAS tags. Substantial effort has been expended inattempts to remedy the deficiencies of radio frequency- andmicrowave-based EAS tags. However, none has substantially improved theirperformance as security tags. U.S. Pat. No. 5,517,195 (Narlow et al.),entitled “Dual Frequency EAS Tag with Deactivation Coil,” describes adual frequency microwave EAS tag that includes an antenna circuit havinga diode, and a deactivation circuit. The deactivation circuit respondsto a low energy alternating magnetic field by inducing a voltage in thediode of the antenna circuit so as to disable the diode and the antenna,thereby deactivating the tag. Although useful for some applications, thecapacitor-based tag disclosed in Narlow et al. may leak electricalcharge over time, which could cause the tag to become activatedunintentionally.

Radio frequency EAS tags of the type disclosed in U.S. Pat. No.4,745,401 (Montean et al.) include a magnetic element. The magneticelement alters the tuning of the tag when it has been suitablymagnetized by an accessory device, and thereby blocks the radiofrequency response of the tag. Although these tags have a certainutility, they still do not address the issues of enhanced security andidentification.

Radio frequency identification technology has been developed by a numberof companies, including Motorola/Indala (see U.S. Pat. Nos. 5,378,880and 5,565,846), Texas Instruments (see U.S. Pat. Nos. 5,347,280 and5,541,604), Mikron/Philips Semiconductors, Single Chip Systems (see U.S.Pat. Nos. 4,442,507; 4,796,074; 5,095,362; 5,296,722; and 5,407,851),CSIR (see European document numbers 0 494 114 A2; 0 585 132 A1; 0 598624 A1; and 0 615 285 A2), IBM (see U.S. Pat. Nos. 5,528,222; 5,550,547;5,521,601; and 5,682,143), and Sensormatic Electronics (see U.S. Pat.No. 5,625,341). These tags all attempt to provide remote identificationwithout the need for a battery. They operate at frequencies ranging from125 KHz to 2.45 GHz. The lower frequency tags (˜125 KHz) are moderatelyresistant to shielding, but have only limited radio frequencyfunctionality due to bandwidth constraints. In particular, systems basedon these markers generally operate reliably only when a single tag is inthe interrogation zone at a time. They also tend to be relatively bulkyand expensive to manufacture. At higher frequencies, (typically 13.56MHz, 915 MHz, and 2.45 GHz), the added bandwidth available has permittedthe development of systems which can reliably process multiple tags inthe interrogation zone in a short period of time. This is highlydesirable for many product applications. In addition, some of the tagdesigns hold the promise of being relatively inexpensive to manufactureand therefore more attractive to a customer. However, these higherfrequency devices share to varying degrees the susceptibility toshielding discussed earlier. Thus, they cannot provide the high level ofsecurity demanded in certain applications, such as a library.

From the foregoing discussion, it should be clear that there are anumber of applications for RFID tags in various environments in whichthe identity of the tagged item is important. For example, PCTPublication WO 99/05660, published Feb. 4, 1999 and assigned toCheckpoint Systems, Inc., describes an inventory system using articleswith RFID tags. The preferred embodiment described therein contemplatesthe use of RFID tags in library materials, which may then be checked outautomatically by interrogating the RFID tag to determine the identity ofthe material. However, a number of important or desirable library orother inventory functions remain that are not described or suggested inthe '660 publication.

SUMMARY OF THE INVENTION

The present invention relates to RFID devices, including handheld RFIDdevices, and applications for such devices. The devices and applicationsmay be used in connection with items that are associated with an RFIDtag, and optionally a magnetic security element. The devices andapplications are described with particular reference to librarymaterials such as books, periodicals, and magnetic and optical media.Other applications for the present invention are also envisioned.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail with reference tothe attached Figures, in which like numbers represent like structurethroughout the several views, and in which

FIGS. 1A and 1B are schematic illustrations of radio frequencyidentification tags;

FIG. 2 is a schematic of a second embodiment of a radio frequencyidentification tag;

FIG. 3 is a schematic top view of a combination tag;

FIG. 4 is a block diagram of an RFID interrogation system interactingwith an RFID tag;

FIGS. 5, 6, 7, and 8 are illustrations of combination tags according tothe present invention; and

FIGS. 9, 10, 11, 12, 13, and 14 are illustrations of various embodimentsof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention described herein make use ofRFID tags, and preferably of combination RFID/magnetic security tags.Tags of this type were disclosed in U.S. application Ser. No.09/093,120, filed Jun. 8, 1998 and entitled “Identification Tag WithEnhanced Security,” which was assigned to the assignee of the presentinvention and was incorporated by reference into the U.S. applicationfrom which the present application claims priority. A detaileddescription of the magnetic, RFID, and combination tags used inconjunction with the embodiments of the present invention is describedin Section I, below, and the embodiments of the present invention arethen set forth in detail in Section II, below.

I. Tags and Elements For Use With Embodiments of the Present Invention

A tag used with the embodiments of the invention described in SectionII, below, may incorporate both object identification and effectivesecurity in a single device. They preferably include an element that isresponsive to a magnetic interrogation signal, and an element that isresponsive to a radio frequency interrogation signal. In one embodiment,the magnetically-responsive element also provides the antenna for theradio frequency-responsive element. The term “responsive” means, in thecontext of the present invention, that the element provides intelligibleinformation when subjected to an appropriate interrogation field. Theindividual elements are described first below, followed by a descriptionof a combination tag. As will become apparent, the embodiments of thepresent invention described in Section II, below, may include either anRFID element alone, or a combination of an RFID element and a magneticsecurity element.

A. The Magnetically-Responsive Element

The magnetically-responsive element is preferably made of a low coerciveforce, high permeability ferromagnetic material, such as the materialused in the strips sold by the Minnesota Mining and ManufacturingCompany of St. Paul, Minn. (3M) under the designation “TATTLE-TAPE™”brand strips. These strips, or marker assemblies, are described inseveral patents assigned to 3M, including U.S. Pat. Nos. 5,331,313(Koning) and 3,747,086 (Peterson), the contents of which areincorporated by reference herein. Exemplary low coercive force, highpermeability ferromagnetic materials include permalloy (a nickel/ironalloy), and high performance amorphous metals such as those availablefrom the AlliedSignal Company of Morristown, N.J. under the designationsMetglas 2705M and Metglas 2714A.

The magnetically-responsive element may be either single status or dualstatus, depending on the nature of the article with which the element isassociated. For example, certain reference books in libraries are not tobe removed from the library, and thus a single-status(non-deactivatable) marker would always indicate whether such a bookpassed within an interrogation zone. Other articles, such as commonlibrary materials or commercial goods, may require a dual-status markerassembly, so that when the article has been properly processed themarker may be appropriately deactivated to prevent detection by theinterrogation source. Dual status functionality is generally providedthrough the addition of sections of higher coercivity magnetic materialin proximity to the low coercivity magnetic material, as described belowand in the Peterson patent incorporated by reference above.

Certain magnetically-responsive elements have the ability to switchmagnetic orientation rapidly when passed through a low frequencyalternating magnetic field (50 Hz to 100 KHz, for example), and toproduce a predetermined characteristic response that may be detected bythe receiving coils of a detector. The switching function of the markerassembly is controlled by the magnetization state of the high coerciveforce elements, or “keeper elements.” When these keeper elements aremagnetized, the ability of the marker to magnetically switch back andforth within the alternating magnetic field of the interrogation zone isaltered, and the marker typically is not detected. When the keeperelements are demagnetized, the marker can again perform the switchingfunction, enabling the interrogation source to detect the presence ofthe marker. The keeper elements may be provided in different ways, as isknown in the art.

The marker assembly may also include adhesive on one or both sidesthereof, to enable the marker to be bonded to a book or other article.The adhesive layer(s) may be covered by a removable liner, to preventadhesion of the marker to an unintended surface prior to application tothe intended surface. These and other features of the marker assemblyare described in the U.S. Pat. Nos. 3,790,945 (Fearon), 5,083,112(Piotrowski), and 5,331,313 (Koning), all incorporated by referenceabove.

Because low frequency magnetic elements of this type are difficult toshield from detection, they may be effectively used on a wide variety ofitems when security is important. In addition, they may be deactivatedand reactivated more conveniently, completely, and repeatedly thanmarkers employing other EAS technologies, making them more suitable foruse in certain applications (such as libraries) where thischaracteristic is highly desirable.

B. The Radio Frequency-Responsive Element

RFID tags can be either active or passive. An active tag incorporates anadditional energy source, such as a battery, into the tag construction.This energy source permits active RFID tags to create and transmitstrong response signals even in regions where the interrogating radiofrequency field is weak, and thus an active RFID tag can be detected atgreater range. However, the relatively short lifetime of the batterylimits the useful life of the tag. In addition, the battery adds to thesize and cost of the tag. A passive tag derives the energy needed topower the tag from the interrogating radio frequency field, and usesthat energy to transmit response codes by modulating the impedance theantenna presents to the interrogating field, thereby modulating thesignal reflected back to the reader antenna. Thus, their range is morelimited. Because passive tags are preferred for many applications, theremainder of the discussion will be confined to this class of tag. Thoseskilled in the art, however, will recognize that these two types of tagsshare many features and that both can be used with this invention.

As shown in FIG. 1, a passive radio frequency-responsive element 10typically includes two components: an integrated circuit 12 and anantenna 14. The integrated circuit provides the primary identificationfunction. It includes software and circuitry to permanently store thetag identification and other desirable information, interpret andprocess commands received from the interrogation hardware, respond torequests for information by the interrogator, and assist the hardware inresolving conflicts resulting from multiple tags responding tointerrogation simultaneously. Optionally, the integrated circuit mayprovide for updating the information stored in its memory (read/write)as opposed to just reading the information out (read only). Integratedcircuits suitable for use in RFID markers include those available fromTexas Instruments (in their TIRIS or TAG-IT line of products), Philips(in their I-CODE, MIFARE and HITAG line of products), Motorola/Indala,and Single Chip Systems, among others.

The antenna geometry and properties depend on the desired operatingfrequency of the RFID portion of the tag. For example, 2.45 GHz (orsimilar) RFID tags would typically include a dipole antenna, such as thelinear dipole antennas 14 shown in FIG. 1A, or the folded dipoleantennas 14 a shown attached to the radio frequency responsive element10 a in FIG. 1B. A 13.56 MHz (or similar) RFID tag would use a spiral orcoil antenna 14 b, as shown attached to the radio frequency responsiveelement 10 b in FIG. 2. In either ease, the antenna 14 intercepts theradio frequency energy radiated by an interrogation source. This signalenergy carries both power and commands to the tag. The antenna enablesthe RF-responsive element to absorb energy sufficient to power the ICchip and thereby provide the response to be detected. Thus, thecharacteristics of the antenna must be matched to the system in which itis incorporated. In the case of tags operating in the high MHz to GHzrange, the most important characteristic is the antenna length.Typically, the effective length of a dipole antenna is selected so thatit is close to a half wavelength or multiple half wavelength of theinterrogation signal. In the case of tags operating in the low to midMHz region (13.56 MHz, for example) where a half wavelength antenna isimpractical due to size limitations, the important characteristics areantenna inductance and the number of turns on the antenna coil. For bothantenna types, good electrical conductivity is required. Typically,metals such as copper or aluminum would be used, but other conductors,including magnetic metals such as permalloy, are also acceptable andare, in fact, preferred for purposes of this invention. It is alsoimportant that the input impedance of the selected IC chip match theimpedance of the antenna for maximum energy transfer. Additionalinformation about antennas is known to those of ordinary skill in theart from, for example, reference texts such as J. D. Kraus, Antennas (2ded. 1988, McGraw-Hill, Inc., New York).

A capacitor 16 is often included to increase the performance of themarker, as shown in FIG. 2. The capacitor 16, when present, tunes theoperating frequency of the tag to a particular value. This is desirablefor obtaining maximum operating range and insuring compliance withregulatory requirements. The capacitor may either be a discretecomponent, or integrated into the antenna as described below. In sometag designs, particularly tags designed to operate at very highfrequencies, such as 2.45 GHz, a tuning capacitor is not required. Thecapacitor is selected so that, when coupled to the inductance providedby the antenna, the resonant frequency of the composite structure, givenby: $f_{r} = {( \frac{1}{2\pi} )\sqrt{\frac{1}{LC}}}$

where

C=capacitance (in Farads)

L=inductance (in Henries)

closely matches the desired operating frequency of the RFID system. Thecapacitor may also be a distributed capacitor as described in U.S. Pat.Nos. 4,598,276 (Tait et al.) and 4,578,654 (Tait et al.), which areassigned to 3M. Distributed capacitance is desirable to reduce tag size,particularly thickness, and to minimize manual assembly.

In operation, as shown in FIG. 4, the radio frequency-responsive tag 110is interrogated by an EAS security system 100, which is typicallylocated near the point at which the tags are to be monitored. Aninterrogation zone may be established by placing spaced detection panelsacross the exits from the room in which the tagged articles are located,near a conveyor carrying items to be monitored, or the like. Hand helddetection devices may also be used. An interrogation source 102(typically including a drive oscillator and an amplifier) is coupled toan antenna 104 (sometimes described as a field coil) for transmitting analternating radio frequency field, or interrogation signal, in theinterrogation zone. The system 100 also includes an antenna forreceiving a signal (shown as antenna 104, and sometimes described as areceiving coil) and detector 106 for processing signals produced by tagsin the interrogation zone.

The interrogation source 102 transmits an interrogation signal 200,which may be selected within certain known frequency bands that arepreferred because they do not interfere with other applications, andbecause they comply with applicable government regulations. When theradio frequency-responsive element receives an interrogation signal ittransmits its own response code signal 202 that is received by theantenna 104 and transmitted to detector 106. The detector decodes theresponse, identifies the tag (typically based on information stored in acomputer or other memory device 108), and takes action based on the codesignal detected. Various modifications of the illustrated system areknown to those of skill in the art including, for example, usingseparate antennas for the interrogation source 102 and the detector 106in place of the single antenna 104 that is illustrated.

Modern RFID tags also provide significant amounts of user accessiblememory, sometimes in the form of read-only memory or write-once memory,but more preferably offering the user the ability to repeatedly updatethe memory by rewriting its contents from a distance. The amount ofmemory provided can vary, and influences the size and cost of theintegrated circuit portion of an RFID tag. Typically, between 128 bitsand 512 bits of total memory can be provided economically. For examplean RFID tag available from Texas Instruments of Dallas, Tex., under thedesignation “Tag-it” provides 256 bits of user programmable memory inaddition to 128 bits of memory reserved for items such as the unique tagserial number, version and manufacturing information, and the like.Similarly, an RFID tag available from Philips Semiconductors ofEindhoven, Netherlands, under the designation “I-Code” provides 384 bitsof user memory along with an additional 128 bits reserved for theaforementioned types of information.

This user accessible memory may be exploited to enhance the performanceof an item identification system deployed, for example, in a libraryenvironment. Presently, libraries identify items by scanning an opticalbarcode. The unique identifier contained in this barcode is used toaccess a circulation database including software provided by libraryautomation vendors (LAV software), where more extensive informationabout the item is permanently maintained. While this system has beenhighly developed and works very well in many applications, it may havetwo disadvantages. First, a connection to the circulation database mustbe established to access the information. This limits the availabilityof the information when an item is at a location remote from aconnection to this database. Second, the retrieval of information fromthe circulation database can sometimes require an unacceptably longtime, particularly during periods of heavy use. By storing certaincritical items of information on the RFID tag, both of these limitationscan be overcome.

One example of information which could improve the performance of alibrary identification system if present on the RFID tag itself would bea library identification number. Then, without accessing a database, anitem's “home” library could be quickly and conveniently determined bysimply scanning the RFID label. Another example of informationpreferably present on an RFID tag itself would be a code designatingwhether the item was a book, a video tape, an audio tape, a CD, or someother item. This code could, for example, comprise the media type codespecified in the 3M Standard Interchange Protocol, which is availablefrom the assignee of the present invention. By immediately knowing themedia type, a library's material management systems could insure that anitem was being appropriately processed without incurring the delay andinconvenience of consulting a remote circulation database. Otherexamples of information suitable for incorporation into the RFID labelwill be apparent to those skilled in the art.

Another area in which RFID systems offer an advantage over barcode-basedsystems is in the identification of multiple items. By usingsophisticated software algorithms, RFID readers and markers cooperate toinsure that all items in the reader's interrogation zone aresuccessfully identified without intervention by the operator. Thiscapability enables the development of numerous useful applications inthe areas of inventory control, item tracking, and sorting that would bedifficult or impossible to implement with barcode-based identificationsystems.

C. The Combination Tag

As shown in FIGS. 3 and 5 through 8, the combination tag 20 combines amagnetically-responsive element with an RF-responsive element to providethe advantages of both. Thus, the two elements can be applied to an itemof interest at the same time, thereby reducing cost. The combination tagmay be provided with a pressure sensitive adhesive covered by aremovable liner, which enables the combination tag to be adhered to asurface of the article when the liner has been removed. In anotherembodiment, the tag uses the magnetically-responsive element as anantenna for the radio frequency-responsive element. Themagnetically-responsive element, when used as an antenna, iselectrically coupled to the radio frequency-responsive element, and mayor may not also be physically coupled to the radio frequency-responsiveelement.

The combination tag made according to the present invention may beinterrogated two ways. First, the RFID interrogation source would useradio frequency signals to request and receive codes from the integratedcircuit. This information would indicate, for example, theidentification of the article with which the tag is associated, andwhether the article had been properly processed. Second, a magneticinterrogation field would interrogate the tag to determine whether themagnetic portion of the marker assembly was active. If the markerassembly was active, the interrogation source would produce a response,such as a notification that the marked article had not been properlyprocessed. Because the magnetic interrogation is more resistant toshielding than the radio frequency interrogation, the magnetic portionof the combination tag would provide enhanced security. Thus, thefeatures of both magnetic and RFID tags are combined into a singlecombination tag.

In a preferred embodiment, the combination tag includes amagnetically-responsive element that also functions as the antenna inthe circuitry of the radio frequency-responsive element. To serve bothfunctions, the antenna material must exhibit low magnetic coercivity andvery high magnetic permeability (to serve as an efficient securityelement), and moderate to high electrical conductivity (to function asan efficient antenna). In addition, the geometry of the antenna must becompatible with both functions. In this embodiment, the antenna could,for example, be fabricated from permalloy, an alloy of nickel and iron.

In one embodiment, a 3M “Tattle-Tape™” brand security strip, or otherequivalent magnetic element, may be used as a linear dipole antenna tooperate at 2.45 GHz or a similar high frequency. The length, width andthickness of this strip are selected to match the particular operatingfrequency and other characteristics of the RFID chip used. Typically,the strip would be made from permalloy (available from a number ofsources including Carpenter Specialty Alloys, Reading, Pa., under thetrade name “HyMu80”) or an amorphous alloy such as that available fromthe AlliedSignal Company of Morristown, N.J., under the designation2705M, and its length would be between 6.35 and 16.5 cm (2.5 and 6.5inches). The terminals of the integrated circuit would be physicallyconnected to the ends of the security strip. Electrical measurements ofimpedance and power gain have established that such a magnetic stripprovides the same fundamental electrical characteristics as the copperor aluminum dipole antennas normally used with such a chip, and thus itwould be expected to perform both functions satisfactorily.

When the magnetically-responsive element is used as at least part of theantenna for the radio frequency-responsive element, the two areelectrically coupled to each other. Electrical coupling may occurbecause of a physical connection between multiple elements (as shown inFIG. 5), or, in the absence of a physical connection, by non-contactelectromagnetic coupling (as shown in FIGS. 6, 7, and 8). Non-contactcoupling can include parasitic coupling, capacitive coupling, orinductive coupling, and use such antenna components as parasitic antennaelements, reflector and director antennas, Yagi-Uda antennas, or othersuitable antenna configurations.

The combination tag shown in FIG. 3 includes coil turns made frommagnetic material. The tag could be, for example, a 13.56 MHz tag havingan antenna structure such as 14 c in which flux collectors are providedat the corners to improve the magnetic function of the tag. Other typesof flux collectors may be provided.

The combination tag 20 shown in FIG. 5 includes a physical connectionbetween the antenna 22, which is made of magnetically-responsivematerial, and the integrated circuit 12. One or more keeper elements orthe type described above also may be applied to themagnetically-responsive material, so that it may be selectivelyactivated and deactivated to provide a dual status tag. The antenna 22 ashown in FIG. 6, however, is not physically connected to the integratedcircuit 12 or the dipole antenna 23, but is nonetheless electricallycoupled to the dipole antenna by parasitic dipole coupling to provide acombination tag 20 a. The dipole antenna 23 may comprise eithermagnetically-responsive material or non-magnetically-responsivematerial.

FIGS. 7 and 8 illustrate embodiments in which more than one antenna 22is provided to electrically couple with antennas 23 b and 23 c,respectively. In the combination tag 20 b shown in FIG. 7, integratedcircuit 12 includes dipole antenna 23 b, which is parasitically coupledto antennas 22 b. Antennas 22 b are made of magnetically-responsivematerial, and antenna(s) 23 b may be made of magnetically-responsivematerial. In the combination tag 20 c shown in FIG. 8, a radiofrequency-responsive element of the type shown in FIG. 2 isparasitically electrically coupled to antennas 22 c. Antennas 22 c aremade of magnetically-responsive material, and antenna(s) 23 c may bemade of magnetically-responsive material. Other variations of theseembodiments are easily designed.

The overall thickness of the combination tag should be as small aspossible, to enable the tag to be inconspicuously placed on or in anarticle. For example, the tag may be applied with adhesive between thepages of a book, and it is desirable to make the tag thin enough toprevent easy detection by observing the end of the book. ConventionalICs may be approximately 0.5 mm (0.02 in) thick, and the overallthickness of the tag is preferably less than 0.635 mm (0.025 in).

The combination tags of this invention may be provided in roll form, toenable the automated sequential application of individual tags toarticles. This general system is described in, for example, PCTPublication No. WO 97/36270 (DeVale et al.). Individual combinationtags, one or more surfaces of which may be covered by an adhesive (suchas a pressure sensitive adhesive), may be removed from the roll andapplied between two pages of a book, near its binding. A page spreadermay be provided to facilitate insertion of the combination tag, andother options such as sensors to detect the position of variouscomponents in the system may also be provided.

The combination tag is believed to have particular, although notexclusive, use in the processing of library materials. Library materialshaving an RFID tag of this type could be checked in and out more easily,perhaps without human assistance. That is, the materials wouldautomatically be checked out to a particular patron (who may herselfhave an RFID tag associated with her library card) when the patronpasses through a suitable detection zone, and checked back in when thepatron re-enters the library with the materials. The tag of theinvention may also assist in inventory management and analysis, byenabling library administrators to keep track of materialsinstantaneously and continuously. These and other features of theinvention can, of course, be brought to bear on other applications, suchas materials handling in stores, warehouses, and the like.

In another embodiment, the combination tag could provide dual-statusmarker information both through a magnetic response (indicating whetherthe magnetic features of the tag had been activated or deactivated) andthrough a radio frequency response (indicating, through the use ofappropriate software, whether the database or the memory on the RFIDchip itself showed that the item had been appropriately processed).

The following Examples provide still further information as to the tagsused in the embodiments of the invention described in Section II, below.

EXAMPLE ONE

A combination tag was made in accordance with the present invention. Apermalloy strip produced from an alloy available from the CarpenterTechnology Corporation of Reading, Pa. under the designation “HyMu80”was attached to a test fixture manufactured by Single Chip Systems (SCS)of San Diego, Calif. The strip measured approximately 1.6 mm (0.625 in)wide by 0.0254 mm (0.001 in) thick by 10.16 cm (4 in) long. The testfixture consisted of a standard SCS 2.45 GHz antenna connected to an LEDdiode. The device was designed so that upon exposure to a 2.45 GHz fieldstrong enough to power a typical SCS RFID tag the LED would glow,providing an immediate visible confirmation of the proper operation ofthe power-receiving portion of the device. Upon replacing the standardSCS antenna with the prototype permalloy antenna, the LED illuminated atapproximately the same field strength, confirming the successfuloperation of the prototype.

EXAMPLE TWO

FIG. 3 illustrates another embodiment of an antenna that is believeduseful with a 13.56 MHz RFID design. At this frequency, a coil-typeantenna geometry is preferred. The spiral turns comprising the coil areformed from a magnetic alloy such as permalloy, either by etching(physical or chemical), die cutting, or deposition through a mask. Thestraight “arm” portions of the coil serve also as the magneticallyresponsive elements in this design. However, the reduced length of thesemetallic elements in this geometry limits the effectiveness of themagnetic security portion of the device. In the embodiment shown in FIG.3, flux collection elements provided at the corners have been added tothe antenna coil to overcome this limitation. The construction shown inFIG. 3 would, preferably, include a capacitor as previously described totune the operating frequency of the antenna to the prescribedinterrogation frequency.

The characteristics of the antenna described in this example werecompared with the characteristics of known antennas for radio frequencyintegrated circuits, and because those characteristics were similar, itis believed that the antenna of this example would function adequatelyin such an application.

The embodiments of the present invention described below may use eithera tag having only an RFID element, or a combination tag, both of whichare described above.

II. Embodiments of the Present Invention

A. RFID Device with Magnetic Capabilities.

Because RFID tags may be shielded either intentionally orunintentionally by a library patron, it is often important to provideboth RFID and magnetic security elements in the tagged library material,preferably on the same tag. When the magnetic security element is dualstatus, meaning that it may be selectively activated and deactivated,its status is typically changed by the application of a magnetic fieldto that element. Magnetization operations such as this have no effect onlibrary materials such as books and magazines, but can have harmfuleffects on magnetically-recorded media. The inventive RFID device withmagnetic capabilities solves such problems, preferably without anyinvolvement by library staff members.

As shown in FIG. 9, an RFID device is equipped to read information froman RFID tag on an item, such as a patron card, book, or other material.Preferably, the information read from the RFID tag includes adesignation of media type (magnetic, print, or optical, for example),which can be used to insure the proper subsequent processing of theitem. The RFID device is also equipped with a device, such as the coil,designed to enable the activation and deactivation of the securityelement portion of the item tag. After the RFID device reads the RFIDtag, the device transmits the item identification information to acomputer having software provided by a library automation vendor, orLAV. Among approximately 50 current LAV software systems are “Dynix,”which is available from Ameritech Library Services of Provo, Utah, “CarlILS” which is available from CARL Corporation of Denver, Colo., and“DRA,” which is available from DRA, of St. Louis, Mo.

There are a number of ways to transmit the information obtained from anRFID tag to the LAV system. One would involve using the commandsimplemented in the 3M Standard Interchange Protocol (SIP). Another wouldinvolve using an electronic device known as a “wedge” to transmit theinformation as if it originated from a conventional barcode scanner.These and other techniques are well-known to those skilled in the art.In this manner, the RFID component of the RFID device performs thefunctions formerly performed by an optical bar-code scanner, which mayor may not continue to be used with the device. Thus, libraries maycontinue to use their existing LAV software system interfaces andterminals while enjoying the added functionality and features providedby RFID technology. The RFID device need not include a display if itwould cooperate with an existing LAV software system display to providefeedback to the operator. Optionally, a display and other feedbackmechanisms may be included in the RFID device as an integrated package.

In devices having both RF and optical bar code reading capabilities, thedevice should be able to handle library materials tagged with RF tags,bar code labels, or both. In operation, the device would process an itemfor check-in by scanning for an RFID tag, a barcode, or both, retrievingthe item identification code and, preferably, the media type from one orboth of these tags, and passing this information on to the LAV softwaresystem. When the device includes both an RFID system and an optical barcode scanning system, the device may also be used to create RFID tagsfor media that is, only bar-coded. First, the bar code would be scanned,and then the identifier (or an ID code associated with that identifier,depending on system design) would be written to (recorded onto) the RFIDtag along with other data, such as media type and other selectedinformation returned from the LAV software system relative to thatmedia. The RFID tag could then be applied to the item.

The RFID device of the present invention preferably also performs“smart” resensitizing and desensitizing of the magnetic securityelements attached to library materials. When the device reads the RFIDtag and transmits the identification information to the LAV software,the LAV software can be programmed to respond with an indication of thetype of library material with which the RFID tag is associated. If theLAV software responds with an indication that the tagged material issomething for which a specialized magnetization operation is required(magnetically-recorded media, typically), then the device can activateonly the system that performs that operation. For example, if the LAVsoftware indicates that the RFID tag is associated with an ordinarybook, and that the book may be checked out by the requesting patron,then one magnetization system may be activated to deactivate themagnetic element associated with that book. However, if the LAV softwareindicates that an RFID tag is associated with a video tape, for example,then a different magnetization system may be activated to deactivate themagnetic security element associated with that video tape. Thisdifferent magnetization system might involve, for example, a weakermagnetic field or a field confined to the region in the immediatevicinity of the security element, so as to prevent damage to themagnetic media itself, depending on the detailed characteristics of thesecurity tags in use. Depending on the detailed design of the device,the procedure might include inhibiting automatic activation so as not todamage magnetic media.

Preferably, sufficient information may be stored in the memory of theRFID tag itself that the interrogation source need not transmit thatinformation to the LAV software, and can instead invoke the appropriatemagnetization system directly. This embodiment would likely improvesystem performance, because fewer steps are required to reach the sameresult. As a minimum, the RFID tag should store a media type in thememory of the RFID element, but could as noted above include additionalinformation. This type of processing, without transmission back to adatabase separate from the RFID device, is referred to herein ashappening in “real time.”

An advantage of an RFID device such as that described is that it mayaccept and process items with less dependence on their orientationrelative to the device. Thus, although a library material may beprocessed by an optical bar code scanner only when the bar code label isproperly positioned and readable by the scanner, a book having an RFIDtag or combination tag may be positioned with front cover either up ordown, and without the need to carefully align a label with a scanner.This advantage of RFID systems over conventional optical and bar codesystems results in considerable time savings for patrons and librarystaff. The “read range” may be different with different scanners, tags,and other components, but it is believed that a read range ofapproximately 15 centimeters (6 inches) would be satisfactory. Tofacilitate reliable RFID scanning, however, it may be desirable toposition the RFID tags for various items at the same fixed positionrelative to an edge of the item. For example, RFID tags provided onlibrary books might all be positioned 2 inches above the bottom of thebook.

The benefits of the inventive RFID device are numerous and significant,and include having only a single station at which to identify,resensitize, and desensitize library materials, the elimination ofoperator training on and performance of different magnetizationoperations, increased processing speed due to the reduction oforientation constraints present in bar-code only systems, and decreasedlikelihood of repetitive stress injury to operators. Another benefit isthat it is faster to scan RFID tags than to read a bar code, especiallyfor codes that are inside the cover or case of the item, in large partbecause the user need not locate and align a bar code. Lastly, thesystem also is a low cost one because RFID readers are expected to costless than high-performance bar-code scanners. These and other benefitsand advantages will be apparent to one of skill in the art.

B. Use of RFID Device with Multiple Items.

Another benefit of an RFID device is the ability to process multipleitems at one time, as shown in FIG. 10. Whereas conventional deviceshaving only optical bar code scanners can process only a single itempresented to the bar code scanner at one time, a group of items havingRFID elements may be processed essentially simultaneously. This may beachieved by having multiple RFID interrogation sources (readers) mountedin or on the device, or by having a single high-speed RFID reader thatpossesses the multi-item identification algorithms. This capabilitygreatly reduces the time required for library staff to process multipleitems.

To avoid having the device perform a magnetization operation that isinappropriate for one or more of a group of materials being processed,the device may be adapted to provide a message to the user requestingthat all materials of a certain kind (books and magazines, for example)be presented together, followed by all materials of another kind (videoand audio tapes, for example). The RFID reader can determine from theinformation obtained from individual RFID elements whether the user hassegregated the materials appropriately, and can prompt the user if he orshe has not, as shown in FIG. 12. In another embodiment, the deviceincludes one area for processing media of one type (books and magazines,for example), and a separate area for processing media of another type(video and audio tapes, for example). The proper magnetization operationmay then be reliably performed as to each material.

The device may also include a display for indicating how many itemsbearing RFID tags have been presented for processing by the device. Thatis, the RFID reader would obtain information from each item presented tothe device, and update the display to indicate that there were, forexample, five items present. An optical or other detector could also beused to verify that the same number of items were indeed present, so asto alert the patron or library staff if an item without an RFID tag hadbeen inadvertently or intentionally included in the stack of othermaterials. Optical detectors of this type may include those described inU.S. patent application Ser. No. 09/058,585 (Belka et al.), filed Apr.10, 1998, now U.S. Pat. No. 6,142,375 and entitled “Apparatus and Methodfor the Optical Detection of Multiple Items on a Platform,” which isassigned to the assignee of the present invention, the contents of whichis incorporated by reference herein. Other detectors may include onesbased on weight (in which the RFID reader can determine from the RFIDtag or the LAV software the weight of the items detected, and compare itto the actual weight of the materials presented), or the number ofmagnetic elements detected (as described in U.S. Pat. No. 5,260,690(Mann et al.), the contents of which is incorporated by referenceherein). Comparison of the number of items detected by the RFID readerand the number detected by an optical or other detector insures that themagnetic security elements associated with non-RFID tagged items are notdeactivated without the item also being charged out to a specificpatron. The device may process the items after a predetermined number ofitems have been presented (five items, for example), or after anoperator instructs the device to process the items, or automaticallywithout any operator intervention. A suitable display may advise theoperator as to the status of the operation.

Another embodiment of the inventive device is the ability to verify thecontent of a package or case having multiple items inside, as shown inFIG. 11. For example, a set of audio tapes may be packaged togetherinside a single case. To insure that only those tapes, and all of thosetapes, are being processed together, the RFID reader can identify thecase, and identify each of the tapes inside the case, and match theidentities before permitting the materials to be checked out to apatron. The RFID tag on the case may include the information as to thecontents of the case, or that information may be stored in the LAVsoftware and accessed through the identification information obtainedfrom the RFID tag.

Devices having the ability to process multiple materials furtherincreases the speed with which materials may be checked into and out ofa library. The device may be adapted to transmit only a single signal tothe LAV software system to process multiple items, and to receive only asingle signal back from that software in response.

C. Portable RFID Devices.

For a number of applications, it is desirable to provide a portable,preferably hand-held, RFID device. The hand-held RFID device is capableof searching among shelves, bins, piles and library carts. It canessentially search wherever it can be positioned close enough to theitems. It is capable of identifying multiple items that are within therange of the device. These and other features make the inventiveportable RFID device a valuable library tool. For simplicity, portableRFID devices will be described first in terms of their components andoperation, and second in terms of various useful functions for ormethods of using such devices. It is important to note that thefunctions or methods described herein are equally applicable tonon-portable RFID devices, and that the functions or methods describedabove in reference to non-portable RFID devices are similarly applicableto portable RFID devices. The different functions and methods havemerely been grouped together with the type of RFID device more oftenused to perform that function or method.

1. Components and Operation. The hand-held RFID device of the presentinvention preferably includes an RFID reader and writer, memory, a powersource, and software to enable various functions of the types describedherein. The RFID reader/writer could consist of a Commander 320 13.56MHz RFID reader, manufactured by Texas Instruments of Dallas, Tex.Memory, preferably in the form of a computer, may be provided by, forexample, a “palm-top” or handheld computer available from 3Com Companyof Santa Clara, Calif. under the designation Palm Pilot. The portablecomputer may include an operating system, a touch-screen display,several buttons for developing user interfaces, a recharge station, adocking station to transfer data between the device and anothercomputer, one or more ports to connect peripherals to the hand-helddevice (such as an RFID reader) and a battery power supply. Some unitsmay also include a built-in peripheral such as a bar-code scanner. Itmay also contain various feedback systems, including lights, audio and adisplay.

As described above, there are a number of options for transferring databetween the hand-held device and another processing station. A dockingstation approach can be used to upload or download data, as shown inFIG. 14. This method could be used, for example, to upload itemidentification information prior to performing a search to find thosespecific items. Another example would be to download data following acollection of items that have been used within the library. The linkcould be implemented as a docking station (as illustrated); as awireless or cabled download and/or upload; as a wireless or cabled,real-time link between the hand-held device and another processor, or inany other manner suitable for transferring such data. One such exampleis a SPECTRUM24 wireless LAN system, from Symbol Technologies ofHoltsville, N.Y. Systems like the Spectrum24 allow mobile users towirelessly communicate between mobile devices and local area networks.For this operation, the mobile unit will typically include acommunication component to support wireless communication, such asSymbol's LA 2400 Wireless LAN PC Card.

The user interface for the device is designed both to communicate thestatus of searching and to allow the user to enter data. Entering datamay include switching the device among various search modes and enteringdata specific to a task (for example, to check out an item, or to put anitem on hold). Feedback to the user is preferably provided through acombination of sound, lights and a display. The display may either beintegrated into the unit or separated. When separate, it can be designedin various ways, including as a “wearable” display that can be easilyviewed by the user.

A particularly useful embodiment of the hand-held RFID device is asfollows. A hand-held RFID device is provided in which the RFID reader,user interface, power source, antenna, processor, and software are allprovided in a single integrated unit, as shown in FIG. 13. By using ahand-held computer such as the Palm Pilot described above, a number ofreal-time functions of the type described below can be achieved, incontrast to systems in which the RFID device must interact with aseparate computer, database, software system, and the like. The softwarecan also provide either limited or full-range capabilities forsupporting functions of the type described herein, as desired. Thehand-held RFID device also preferably includes an integral power source,although it can be tethered to a larger power source of the type thatmight be worn around a user's waist. In the case of an integral powersource, the source may or may not power the processor, and may berecharged when connected to a docking station. When a hand-held computeris used, it may include its own power source, and may be recharged whenconnected to the docking station to upload and/or download information,as shown in FIG. 14.

A hand-held RFID device can interrogate and identify RFID-tagged itemswhenever it is activated within range of the items. Intermittentactivation can be provided by, for example, a trigger associated withthe device, so that the elapsed time for which power is required for theRFID device is minimized. The reading distance is a function of manyfactors, but is expected to be between 15 and 45 centimeters (6 and 18inches) given current technology and the likely frequencies at which thesystem would operate. In some applications, it may be desirable torestrict the operating range of the device so that it only interrogatesRFID tags associated with items at a closer range. In other cases, thelongest available range of operation will be desired. In otherapplications, it may be preferred to restrict the output power (and thusthe reading range) to permit longer continuous operation from thebattery pack. The read range will also be influenced by the design ofthe antenna as well as the orientation of the RFID tag relative to theantenna. It should be appreciated that the read range, battery weight,and lifetime between battery recharges or replacement are oftendependent on each other. Various tradeoffs can be envisioned, based onthe particular application for the device.

In operation, a particularly useful feature of a hand-held device isobtaining real-time information regarding an item that has been scannedby the device. That is, the hand-held device obtains information fromthe RFID tag, and either immediately displays that information, orimmediately displays information stored within the hand-held device thatis related to the tagged item. This is in contrast to devices that mustbe docked with or otherwise communicate with a separate database ofinformation before that information can be displayed for the user. Thehand-held device of the present invention can also be docked or canotherwise communicate with a separate database, if such features aredesired.

2. Functions, Methods, and Applications. The hand-held RFID device ofthe present invention can be used for a number of functions, methods,and applications, including the following.

The inventive handheld RFID device has particular usefulness in itemlocation. For example, the device could be programmed with specificinformation identifying certain items that an operator wishes to locate.The unique identifier for each desired item would be stored in areserved memory location in the handheld computer. As the identifiersof, for example, items on a shelf were read by the RF reader, each wouldbe compared, using standard software routines known to those skilled inthe art, with the list of items stored in memory. When a match occurred,the device would then create one or more visual, audio, tactile, orother signals indicating the presence of the item. One application forthis function includes locating items that are believed to be missing. Alibrary typically maintains a list of missing items—those items that areexpected to be in the library, but cannot be found. By downloading thosemissing item identifiers to the hand-held device, the operator can passthe device by items and obtain feedback when a missing item isencountered.

Another example is to locate items that have not circulated or been usedwithin a given number of months. Again, the identifiers of those itemscould be downloaded to the hand-held device for searching.Alternatively, the circulation counts can be maintained directly on thememory of the RFID tag. In this case, the hand-held device does not needto download any data from another computer system. The hand-held deviceonly compares RFID memory data to established criteria and providesfeedback to the operator based on the selected parameters.

Another example of where data can be either downloaded from a librarydata base to the hand-held device or obtained directly from the RFID tagis to locate items in the library that have not been checked in. A listof items not checked-in could be obtained and then downloaded to thehand-held device or the RFID tag could maintain a memory location toindicate the check-in status of an item. When the RFID tag memoryindicates the check-in status, the hand-held device does not need anydata from an external database to perform the search. A naturalapplication of obtaining matching data directly from the RFID tag is tolocate items that belong to different library buildings or to differentlibrary systems. For this application, the owning library is preferablyencoded onto the RFID tag and the hand-held device alerts the operatorwhen an RFID tag with a different owning library code is encountered.The hand-held RFID device could also be used to determine, as with theRFID device described above, whether all members of a set of associateditems are present together, as with the tapes in a books-on-tape case.

The RFID device of the present invention could also be used to verifythe order of materials on a shelf. In this mode, the device is scannedacross one or more rows of items. The device reads each item andindicates, to the operator, which items are not shelved in the correctorder. As input, the device has access to the shelving algorithm used bythe library for the section being scanned. Possible algorithms include:Dewey Decimal order, Library of Congress order, and Author lastname/Title order. Other methods of sorting, as determined by eachlibrary, are possible.

Another method of establishing shelf information is to associate eachitem with a location. Shelf locations can be as specific or as generalas the library desires. For example, a general shelf location mightinclude all “Adult Fiction titles.” A more specific shelf location mightbe “Adult Fiction, Authors AA-AB.” In the preferred embodiment, theshelf location for an item is encoded directly in the RFID tag memoryfor that item. An indexing system may also be used to save memory, sothat a short code number is used to indicate a shelf location. Forexample, the number 1 could represent Adult Fiction, the number 2 couldrepresent Juvenile Fiction, and so on. The amount of memory needed tostore all shelf locations depends on the number of locations within alibrary. Another embodiment is to obtain the desired shelf location froma library database and then download those locations as part of thetransfer of data to the hand-held device.

When items are associated with a shelf location, by either method above,the operator can use the hand-held device to locate items that are inthe wrong location. Two processing methods can be used to determinewhich shelf location is currently being processed in order to search foritems with non-matching locations. In one embodiment, the correct shelflocation is obtained by reading several RFID tags and heuristicallyprocessing the data to infer a location. For example, if the RFID devicereads a certain number of tags that are indexed to the Adult fictionarea, the device can be programmed to alert the user when non-AdultFiction items are encountered. In another embodiment, the library places“location tags” on the shelves or other locations to be searched. Theselocation tags are first read by the hand-held device to indicate thatsubsequent items read should belong to that location and an alert isprovided when a mismatch occurs.

In another embodiment, the hand-held RFID device may be used to enterdata into the device as to a specific item. That information may beeither transmitted immediately and directly to the LAV software, or maybe transmitted subsequently when the hand-held device is reconnected toa docking station and downloads the information to the LAV software. Forexample, when a user takes a library material from its location, theuser may input the new status of the article into the hand-held RFIDdevice. Because this information must be entered into the LAV softwareeventually, it saves the operator time to be able to indicate this statedirectly and immediately as opposed to waiting until he or she canaccess an LAV software system terminal.

In yet another embodiment, the hand-held device could be used to provideadditional information about a specific item once the item has beenobtained and its RFID tag scanned by the RFID device. For example,library staff may collect materials that have been used in the library,and scan those materials either to obtain more information about thatmaterial (who last checked it out; how often has it been used) or toprovide information to a database that generates statistical profiles oflibrary material usage, or both. The operator simply reads the RFID tagsof the items as they are collected from the various locations in thelibrary at which they were used. As items are collected, the operatorcan also indicate from where the items were collected by selecting froma list of locations, entering a location code or reading a “locationRFID Tag” that is associated with that location and would preferably beaffixed to or near that location. In this way, the library staff is ableto obtain additional information about where in the library suchmaterials were used. Alternatively, if items used in the library arefirst placed on a book cart, for example, the hand-held device couldmake a single pass by the items on the cart to record them. Thefunctions described in this paragraph are referred to herein as“sweeping.”

The benefits of a hand-held RFID device are numerous, and include theability to locate items more quickly and accurately compared to readingeach call number or title from items, the ability to “get close” todesired item quickly and then examine items more closely to locate itemof interest, the ability to quickly identify items matching a given setof criteria (lost, not checked out, matching specific circulationvalues, etc.), and the ability to identify items that are mis-shelvedand indicate, to the operator, the correct location for the items. Thiswould include items that don't belong in the collection being scanned.Other advantages include the ability to enter transactions directly intothe hand-held unit when items are located, the ability to identify anitem without having to scan a bar code or any other markings on theitem, such as author, title and call number, and the ability todetermine if a given item is somewhere on a shelf, on a library cart, ina bin, on a table or even in a pile. These and other advantages will beapparent to those of skill in the art.

In the claims appended hereto, persons of ordinary skill will recognizethat the items recited could be library materials (including books,periodicals, magnetic or optical media, and the like), or could be othercompletely unrelated materials such as packages, letters, paintings,electronic devices, animals, automobiles, bicycles, or any other itemsof value.

We claim:
 1. A portable RFID reader comprising an RFID interrogator, anantenna, and a processor, wherein to operating range of the reader isrestricted so that the reader only interrogates RFID tags that are at acloser range than in the absence of to restriction, wherein theoperating range of the reader is restricted by restricting the outputpower of the RFID reader, and wherein the RFID reader is tethered to apower source.
 2. A portable RFID reader comprising an RFID interrogator,an antenna, and a processor, wherein the operating range of the readeris restricted so that the reader only interrogates RFID tags that are ata closer range than in the absence of the restriction, wherein theoperating range of the reader is restricted by restricting the outputpower of the RFID reader, and wherein the RFID reader further comprisesa trigger for intermittent activation of the RFID reader.
 3. A portableRFID reader comprising an RFID interrogator, an antenna, and aprocessor, wherein the operating range of the reader is restricted sothat the reader only interrogates RFID tags that are at a closer rangethan in the absence of the restriction, wherein the operating range ofthe reader is restricted by restricting the output power of the RFIDreader, and wherein the RFID reader verifies the order of materials on ashelf.
 4. The portable RFID reader of claim 3, wherein the order ofmaterials on the shelf is based on a shelving algorithm.
 5. The portableRFID reader as in any of claim 1-3 wherein the RFID reader furthercomprises a user interface that communicates the status of searching andpermits a user to enter data into the RFID reader.